Re: What are keepalives ?

vijayendran · ‎06-07-2003

What are keepalives ?

Are they different from Hello messages used by the dynamic routing protocols ?

If no dynamic routing protocol is used in a network, would these keepalives still be exchanged, if so, how often ?

t.baranski · ‎06-07-2003

Keepalives are generally used between two devices to say "Hello, I'm still here." This is what routing protocol Hello messages do at a basic level, though they tend to contain more information than simple keepalives do.

Keepalives are used by many protocols; they're not confined to routing protocols. High availability protocols (HSRP, VRRP) use them, CDP, Spanning Tree, etc... It's a long list. A lot of data link protocols such as HDLC and Frame Relay also use them to ensure that links are functional. The rate that they are exchanged is protocol-dependant and usually configurable.

vijayendran · ‎06-08-2003

So, are keepalives exchanged by default or should we configure the devices to generate keepalives?

t.baranski · ‎06-08-2003

Protocols/links that require the use of keepalives generally exchange them by default -- simply enabling the protocol or link causes keepalives to be exchanged. The only time you should find yourself having to enable them explicitly is when they're not required for basic functionality, but can add some benefit. Frame Relay End-To-End keepalives and GRE Tunnel keepalives are the only examples that come to mind offhand.

girishvyas · ‎06-09-2003

can u tell me wht are PPP keepalives?

i have configured a PRI ISDN backup for a leased line .channels come up when leased line goes down .but after some time error comes:

PPP: Missed 5 keepalives : bringing LCP Down

and channels get disconnected and again new channels start coming up.

wht does this mean ? and how to avoid it?

t.baranski · ‎06-09-2003

I'd suggest starting a new thread on this issue, and providing the relevant configuration portions of the router(s) involved.

girishvyas · ‎06-10-2003

ya i have done that but still no solution .you can check out conversation-

"ISDN PRI used for backup "

config and debug outputs are pasted there.

but still no help on wht is this error and wht are keepalives in PPP.